This application claims the priority of Swiss application No.385/96, filed on Feb. 14, 1996, the disclosure of which is incorporated herein by reference in its entirety.
The present invention relates to one-component polyurethane (PU) systems, particularly fire-retardant (FR) systems. These systems are preferably halogen-free. The systems can be used as adhesive, sealant or coating materials.
The use of aluminium trihydroxy hydrate (ATH) alone or in combination with a phosphorus or halogen containing compound is known in two-component polyurethane systems. Such a system is described, e.g., in U.S. Pat. No. 4,876,291. That document describes a method for forming a fire-retardant composition that is added to the polyol component shortly before mixing with the isocyanate compound in order to achieve superior physical foam properties. This fire-retardant composition contains a hydrated filler, such as ATH, which is pretreated with 0.25 to 5% polyfunctional isocyanate relative to the amount of ATH, resulting in a moisture content of about 0.2%.
Hydrated minerals, such as aluminium trihydroxy hydrate (ATH) impart both flame and smoke retardancy by evolving non-toxic gases, such as water, to dilute combustion products and to promote char formation.
However, it has been found that a pretreated ATH, such as that described in U.S. Pat. No. 4,876,291, is not suitable for one-component adhesive formulations held in a sealed vessel. There is a lack of storage stability leading to a fast increase in viscosity. As a result, there is a substantial loss of handling properties in a relatively short period of time.
One component polyurethane systems comprising predried additives are known in the art. WO 94/06886, for example, discloses a vitreous filler that is predried using an isocyanate having a functionality of at least 2. FR-A-1,505,924 and FR-A-1,356,972 both describe PU-systems comprising predried pigments. The pre-drying is performed using water-reactive compounds.
The use of aluminium oxide as a drying agent for PU-systems (produced by incomplete dewatering of aluminium oxide trihydrate (aluminium hydroxide) to a water content of 0.5 to 0.05 mole per mole aluminium oxide), is described in FR-1,496,648.
An optionally high pigmented mass (5 to 25% pigment) is described in EP 0 200 801. In addition to the pigment, the mass comprises about 1 to 3% by weight of a moisture binding agent.
Since two component systems are not as easy to use as one component systems, it is one object of the invention to provide a one component, fire-retardant (FR) polyurethane (PU) system, which, most preferably, is halogen-free. It is a further object of the invention to provide a specific manufacturing method to achieve storage-stable fire-retardant adhesives.
Another object of the invention is to provide particulate fillers for imparting flame retardation, which are suitable for use in one-component PU systems.
Accordingly, it is a general object of the present invention to provide isocyanate and/or silane terminated polyurethane systems that are storage-stable, moisture-curing and fire-retardant.
It was surprisingly found to be possible to formulate a flame-retardant and storage-stable, moisture-reactive PU-system containing a considerable amount of hydrated minerals filler material, such as aluminium trihydroxy hydrate (ATH), even in large amounts, e.g. more than 35%, if the hydrated minerals are treated by a particular method which is also part of the present invention.
The desired storage-stability can be achieved by a specific production method for the hydrated mineral wherein a mineral""s surface activity is reduced and neutralized, thus preventing undesired increases in viscosity upon storage (which makes application impossible).
The surface activity of hydrated minerals depends on the groups capable of reacting with NCO-groups of the binder.
It is a further object of the present invention to provide an ecological system that moisture-cures to a flame and smoke retardant elastomer, particularly such a system for use as an adhesive, sealant or coating material.
This was possible through the use of a specially treated hydrated mineral, preferably with a halogen-free, phosphorus-containing substance, preferably a phosphorus-containing plasticizer. Such a phosphorus-containing compound improves the fire-retardant performance of the hydrated mineral, preferably ATH, in an unexpected manner. The phosphorus-containing material may be present in the formulation in a specific ratio relative to the binder. If the phosphorus-containing compound is a phosphorus-containing plasticizer, e.g., diphenylcresylphosphate (DPK), then the ratio of phosphorus-containing plasticizer to binder can be in a range of 0.25 to 5, preferably in a ratio of 0.7 to 1.5, and most preferably is about 1.